1. Field of the Invention
This invention relates to a ball valve of the kind comprising a valve housing in which the valve member of the valve housing is retained between an annular sealing member and an annular retaining element mounted through one of the connecting branches of the valve housing.
2. The Prior Art
Ball valves of the kind referred to above are known wherein the annular retaining element is screwed into contact against the valve member so as to press the valve member against the annular sealing member with a sealing pressure. However, in the previously known ball valves of this kind it has proved to be difficult to obtain the optimum sealing pressure between the annular sealing member and the valve member. It has been proposed to provide the annular retaining element and the valve housing with cooperating abutments which engage upon termination of the screwing-in of the annular retaining element, whereby it should be possible to obtain a well defined sealing pressure between the valve member and the annular sealing member. However, due to unavoidable tolerance variations during the manufacturing of the valves, it is not possible by means of such a valve to secure an optimum sealing pressure.
As regards the prior art reference is also made to U.S. Pat. No. 2,373,628 wherein from which a ball valve is known, the seats consist of rings of molded elastomeric material. In each seat ring a spring insert is embedded having radially projecting fingers. When mounting the seat rings, the fingers are arranged with snap-action in circumferentially extending grooves in the valve housing. However, also in this case tolerance variations during the manufacturing of the valves will cause unequal sealing pressures between the valve member and the seat rings.